Method for manufacturing porous point tip

ABSTRACT

A porous point tip and method for manufacturing same for use in marking instruments which have a soft, velvety brush-like feel when in use. A conventionally manufactured marker tip is subject to a &#34;velvetizing&#34; process by moving the tip relative to an abrasive wheel such as a wire brush and intruding the tip into the brush so as to abrade or roughen the marking face. The present invention is particularly adapted to product tips which have a broad coherent liquid conveying body and an integral soft terminal or end portion rather than the hard pointed tip of conventional writing instruments which produce a fine line trace. In a particular application of the invention, the tip is comprised of one or more slivers of synthetic staple fibers bonded into a porous rod which is subsequently severed to provide a terminal marking face which is then brought into engagement with the peripheral edge portion of the rotating abrasive wheel to fracture the bond between most of the fibers or filaments adjacent the marking face to a depth of from 20 to 50 miles without destroying the integrity of the filaments and without softening the individual filaments to the point at which they become fusible with contiguous filaments sa as to produce a marking face which has a plurality of unbonded filament end portions capable of independent bending while the body of the tip retains it bending strength.

3 H. DAVIDSON 3,714,314

METHOD FOR MANUFACTURING POROUS POINT TIP Filed March 22, 1971 I/vvE/v 70/2 I HEN/4w D0 v/oso/v United States Patent US. Cl. 264-137 5 Claims ABSTRACT OF THE DISCLOSURE A porous point tip and method for manufacturing same for use in marking instruments which have a soft, velvety brush-like feel when in use. A conventionally manufactured marker tip is subject to a velvetizing process by moving the tip relative to an abrasive wheel such as a wire brush and intruding the tip into the brush so as to abrade or roughen the marking face. The present invention is particularly adapted to produce tips which have a broad coherent liquid conveying body and an integral soft terminal or end portion rather than the hard pointed tip of conventional writing instruments which produce a fine line trace. In a particular application of the invention, the tip is comprised of one or more slivers of synthetic staple fibers bonded into a porous rod which is subsequently severed to provide a terminal marking face which is then brought into engagement with the peripheral edge portion of the rotating abrasive wheel to fracture the bond between most of the fibers or filaments adjacent the marking face to a depth of from 20 to 50 mils without destroying the integrity of the filaments and without softening the individual filaments to the point at which they become fusible with contiguous filaments so as to produce a marking face which has a plurality of unbonded filament end portions capable of independent bending while the body of the tip retains its bending strength.

BACKGROUND OF THE INVENTION Various processes for manufacturing continuous, synthetic-fiber rod which may be severed into desired lengths for use as porous point writing or marking tips are known. One such process is described in detail in US. Pat. No. 3,558,392, issued Jan. 26, 1971 to E. L. Goodenow et al. The exemplary method described in detail in that patent is particularly adapted to the manufacture of rod having a circular cross section formed from a plurality of strands of yarn of filamentary material which are gathered, arranged and positioned into a predetermined parallel pattern and is then compacted and heat set to desired cross sectional shape and size and subsequently impregnated with a bonding resin in a solvent and cured. The process of the patent is particularly efficacious in producing hard and strong sharp pointed writing tips for writing instruments capable of leaving a thin fine line trace, whereas the present invention is particularly directed to the production of marker tips which are somewhat larger in cross sectional area and have a soft, velvety end portion which produces a very smooth slightly yielding feel when used as a writing instrument. Tips formed in accordance with the present invention may be used as an applicator for colored fluids and liquid compositions containing cosmetics, such as eye liners, eye shadow, etc. The writing or marking face of a tip manufactured by a conventional process but not subjected to the velvetizing method of the present invention has a relatively hard, smooth and brittle marking surface that results in a hard feel to the user which is often unsatisfactory.

3,714,314 Patented Jan. 30, 1973 SUMMARY OF THE INVENTION In view of the above-described problems with rod used for marker tips manufactured in accordance with the conventional process, it is an object of the present invention to provide a method for manufacture of a marker tip in which the marking face is abraded so as to produce a face which is soft, velvety and brush-like while the remainder of the tip retains its bending strength and integrity. Another object of this invention is to provide such a velvetizing process in which the resinous bond between adjacent synthetic fiber or filament end portions at the marking face of the tip is fractured by intruding the tip marking face into a wire brush wheel to a depth of from 20 to 40 mils and at a speed and for a period of time which is insufiicient to cause softening and possible bonding between adjacent fiber ends. Still another object of this invention is to provide a velvetizing process in which the marking tip produced has a soft, slightly yielding brush-like marking face rather than the hard, smooth and relatively brittle faces that are useable for producing a fine line writing trace but do not have proper marking properties for use in a marking instrument. Yet another object is to provide such a method for preparing the marker tips in a rapid, inexpensive and simple manner commensurate with mass production of marking instruments.

Generally stated, the present invention provides a method for the production of a porous point tip having a soft and velvety marking end face on a high strength relatively harder tip body, the tip being made by compacking and heat setting a multitude of synthetic filaments into a porous, coherent rod, impregnating such rod with a solution of bonding resin, and curing such resin so as to firmly and immovably bond together the filaments comprising cutting the rod into predetermined lengths with end faces disposed at an angle to the longitudinal axis of the rod, and fracturing the resinous bond between most of the filaments terminating at said face to a depth of between 20 and 50 mils from said face without destroying the integrity of such filaments, whereby the end portions of the filaments are capable of virtually independent bending with respect to each other while the remaining portions of the filaments are firmly bonded together to provide a high strength tip body portion having longitudinal extending channels adapted to convey liquid to said face.

BRIEF DESCRIPTION OF DRAWING FIG. 1 is a front elevation view, partly in section, of a marking instrument employing a marking tip constructed in accordance with the exemplary method of the present invention;

FIG. 2 is a perspective view ofa marking tip manufactured by the exemplary process of the present invention;

FIG. 3 is a side elevation view of a portion of a marking tip constructed in accordance with the present invention;

FIG. 4 is a view taken along the plane IV-IV of FIG. 3;

FIG. 5 is a diagrammatic illustration of an exemplary abrading method in accordance with the present invention showing the abrading wheel and tip in side elevation; and

FIG. 6 is a view taken along the plane VI'V='.[ of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Prior to describing the method of manufacture of marking tips in accordance with the present invention,

reference is made to FIG. 1 of the drawing which discloses a marking instrument in which the tip manufactured in accordance with the present invention is used. Such instrument comprises a cylinder 10, an absorbent ink carrying reservoir 20, and a marking tip indicated generally at 30. The container 10 generally comprises a cylinder 11 which may be of plastic material, an integral base 12, and a neck portion 13 on which a cap may be removably secured. The reservoir 20 may be constructed of material and in a manner well known in the art, such as a porous body of polyester, polyamide, polyvinylacetate or polyethylene fibers which may be formed into a cylindrical shape, and inserted within the cylinder in a manner to provide venting of the reservoir body.

- The marking tip 30 may be fixedly mounted in the neck portion 13 and the container 10 by a stake or the like. The tip 30 has an inner end 31 contacting the reservoir 20 so as to receive and supply ink by capillary action to the outer end 32 of the marking tip. A marking face, indicated generally at 33, is provided at both ends 31, 32 of the tip so as to simplify manufacture and to facilitate assembly of the marking instrument. It will thus be understood that while the process to be described hereinafter relates to only one end portion of the tip, an identical process may be simultaneously employed for preparation of the other end of the tip.

The writing face 33 in the exemplary embodiment is generally oblique to the longitudinal axis of the marking tip at an angle A, preferably in the range of 55 to 60 degrees. The marking face 33 may be provided with beveled or chamfered edges 34, 35 along the side edges of the marking face and a chamfered edge 36 at the apex of the tip. Chamfering of the marking face edges may be required to remove the peripheral region of a rod, when manufactured by the conventional rocess, which may have a high resin content that impedes ink flow and prevents the tip from providing a proper laydown or trace. It is to be understood, however, that the method of the present invention is not limited to a marking face that has been beveled or ehamfered. The writing face 33 includes a central region 37 which, if the tip is chamfered, constitutes the portion in engagement with the writing surface.

The ehamfered edge portions 34, 35 may be disposed at an angle, indicated at B, of approximately 45 degrees. The dimension C, as shown in FIG. 3, on the side chamfered edge portions 34, 35 may be approximately 40 mils. 'Ihe ehamfered apex 36 is disposed at an angle D relative to the plane of the marking face central region 37 and may be approximately 95 degrees. The dimension E of the ehamfered apex edge portion 36 (in the plane of the contact face 37) may be approximately 44 mils. The above exemplary ehamfered dimensions and angles for the marking point 30 have been given for a point having a length of approximately 1.2 inches, a cross sectional longitudinal dimension of approximately 220 mils and a lateral dimension of approximately 130 mils. It will be appreciated that the cross sectional area of the marking tip is larger than the cross sectional area of tips used in fine line writing instruments.

With respect to the process or method of manufacture of the rod which is used in marking tips, it is to be understood that although strands of yarn are eminently suited for making fine writing points, marker tips can be ecoomically made by the use of one or more strands of carded synthetic filament staple stock in the form of sliver. When making marking tips for use with water based inks, staple polyester fialments of between about 1 and denier, and of about 1 to 2 inches in length, are satisfactory. A marker tip of the final size indicated above may be made from a sliver having a total denier of between about 50,000 and 65,000. Such sliver is drawn under slight tension through a heat setting zone in which the cross sectional area is reduced and shaped. The rod is then drawn through a dilute solution of a curable resin and a vaporizable solvent so as to impregnate the rod. During impregnation, solution fills approximately all of the voids between the synthetic fibers in the sintered rod. Following saturation, the rod is then passed through an evaporator to remove the methylethyl-ketone or other solvent and leave a minute, discontinuous layer of bonding resin on the fibers. The evaporation may be accomplished by passing air an elevated temperature in a direction counter to the direction of movement of the rod through a tube surrounding the rod so as to accomplish approximately 95 percent evaporation of the solution. If necessary, the rod may be cured in a subsequent step. The resulting rod has substantial bending strength and is relatively hard and comprises a multiude of synthetic filaments in a porous coherent rod with longitudinally extending channels adapted to convey liquid to a marking face. The filaments are firmly bonded together and it is this bond wihch provides the rod bending strength.

The continuous rod is then cut or severed by a rotary saw and is ehamfered using a 40 to 60 grit silicon carbide grinding wheel.

.In accordance with the present invention, the face of the marking tip is then abraded or brushed. It will be understood that the term abraded or brushed refers to the mechanical process of roughening the surface by a scraping, eroding, rubbing, wearing or other frictional action. The abrading takes place while the tip is held or disposed in a suitable holder 41 (see FIG. 5) that may be mounted on an indexing wheel for moving successive tips into position for performing the method of the present invention and with a marking face 33 of a tip disposed in a plane perpendicular to the plane of an abrasive wheel, such as the wire brush wheel 42. The wire brush wheel has a peripheral face 43 which is preferably wider than the tip face and is generally adjacent thereto. The tip and the holder may be moved relative to the wheel which may be maintained stationary on its horizontal axis, or the wheel may be mounted for reciprocal movement relative to the tip marking face. It is important to obtain the results desired that the translational movement between the tip and wheel be in the same direction as the direction of movement of a point on the periphery of the wheel during contact with the marking face. In other words, where the wheel moves from left to right as shown in FIG. 4 during the contact stroke of the reciprocating wheel, the wheel will rotate counterclockwise as shown. It is also important that the abrading engagement take place at the heel 38 of the marking face where the general orientation of the fibers in the rod are oblique and extend in the direction of movement of the wheel and tip. It has been found that introducing the apex 39 of the tip into the wheel causes distortion and deformation of the forward portion of the marking face and leaves a tail at the heel of the marking face which results in unsatisfactory marking laydown characteristics.

The tip marking face is moved relative to the wheel axis in a plane which is generally tangential of the peripheral edge of the wheel but intrudes slightly into the edge portion of the wheel so that such edge portion penetrates into the tip at a preselected depth. It has been found that superior marking characteristics are obtained when the depth of penetration of the peripheral edge portion of the wheel is in the range of 20 to 50 mils. The effect of brushing or abrading has been found to be ineffective unless the penetration is at least 20 mils as determined by the soft feel that is produced when the point is brushed to at least this depth. On the other hand, where the penetration is greater than 50 mils, the marking characteristics of the tip prove to be unsatisfactory because the tip gives a mushy or spongy feel and under normal pressure is likely to dimensionally deform so as to result in a laydown of varying width. In commercial production, the penetration depth has been set for 40 mils which is equal to the chamfer dimension F as shown on FIG. 3.

Abrading of the marking face, besides being dependent upon the tip configuration or shape (including the overall area of the face and the amount of chamfering of the edges), the total denier of the rod, the denier of the individual filaments, and the percentage of epoxy in the impregnation solution, also depends upon the coarseness of the abrasive wheel, the speed of rotation, the diameter of the wheel and thus the tangential speed, etc. The wheel speed and the duration of contact between the wheel and face are particularly critical factors since it is important that the synthetic fiber ends are not heated to the melting point. In an exemplary method, the abrasive wheel 42 may be a wire brush wheel having a diameter of approximately 4 inches with individual wire thickness of approximately 8 mils. The wheel is rotated at a speed in the range of 400 to 500 rpm, with a preference for 450 rpm. The contact duration is in the range of 0.1 to 0.5 second. These parameters have been established for rapid, continuous commercial production of the marking tips having physical characteristics as described above.

It is believed that the brushing results in a fracture of the resinous bonding material between end portions of the slivers thus allowing the end portions of the fibers to flex and bend when the marking instrument is in use. The fractured resinous material may be dislodged from between the fibers and thus removed from the writing face or may remain bonded to one of the fibers while being severed from the contiguous fibers which it has previously bonded together but in any event, such fracturing allows the fibers to independently bend and flex. In the process of cutting the tip from the continuous rod it will be appreciated that many of the staple fibers in the sliver will be severed to a length of 50 mils or less and that in the abrading process these fibers will be dislodged from the end portion of the tip thereby providing added lateral space for bending of the fibers remaining in the tip end portion. Physical observation by the naked eye establishes that prior to brushing, the surfaced (when viewed from the edge) is relatively smooth and hard with no visual voids or open spaces between the fibers whereas after the abrading process minute open spaces between the fiber ends can be seen and the marking contact face is both visually and tactilely brush-like. Microscopic analysis confirms that the end portions of the fibers are free and unbonded after the abrading process. It is important to understand that the abrading or brushing process results in the fracturing and at least partial removal of the resinous bonding material and short fiber ends but does not split or flag the other individual fibers, which remain intact with their inner portions bonded together to form a rigid, strong body portion having longitudinally extending and interconnecting liquid conveying channels.

In the preferred exemplary embodiment, applicant has shown the process described with respect to polyester filaments or fibers. Applicant has also used the process with nylon filaments and it should be emphasized that any thermoplastic synthetic filament can be utilized with equally satisfactory results.

Through the use of the limitations and sequence of steps of the above-defined process on marking tips having the physical characteristics as disclosed, marking tips can be manufactured in a controlled manner with assurance they will have proper writing properties. Obviously, changes and modifications may be made to the present invention in light of the above teachings.

I claim:

1. A method of providing a soft and velvety marking face on a strong and hard body portion of a marking tip made by compacting and heat setting a multitude of synthetic filaments into a porous, coherent rod, impregnating such rod with a solution of bonding resin, and curing such resin, the filaments being firmly and immovably bonded together by said resin, comprising:

cutting said rod into predetermined lengths to provide each length with a marking face disposed at an angle to the longitudinal axis of the rod;

disposing the marking face in a plane perpendicular to the plane of an abrasive wheel having a peripheral face wider than the tip face and adjacent the tip face; rotating the abrasive wheel in a first direction at a speed in the range of from 400 to 500 rpm;

relatively moving the tip face and said wheel in said first direction along a plane generally tangential to the peripheral edge of the wheel; and

intruding the tip face into the peripheral edge portion of the wheel so that the peripheral edge portion penetrates into the tip a depth of between 20 and 50 mils from the face for a period in the range of from 0.1 to 0.5 second, thereby fracturing the bond between the end portions of the filaments whereby the end portions of filaments are capable of virtually independent bending with respect to each other while the remaining portions of the filaments are firmly bonded together to provide a strong body portion having a longitudinally extending channel adapted to convey liquid to said marking face.

2. The method of claim 1 wherein said abrasive wheel is a wire brush wheel having a diameter of approximately inclhes, and individual wire thickness of approximately 3. The method of claim 2 wherein the tip is oriented so that the heel of the tip is first brought into contact with the brush wheel.

4. The method of claim 3 wherein said wheel periphtlaral edge penetrates the tip a depth of substantially 40 mi s.

5. The method of claim 4 including an additional step of chamfering the edge portions of the marking face subsequent to cutting of the rod into the predetermined lengths and prior to fracturing the resin bond between the filaments.

References Cited UNITED STATES PATENTS 3,467,564 9/1969 Daugherty 156--154 3,597,256 8/1971 Young 1178 2,905,971 9/ 1959 Valentini 264-162 1,881,337 10/1932 Willis 264-162 X 3,538,208 11/1970 Ohtsuka 264-89 3,615,990 10/ 1971 Butler 2627 ROBERT F. WHITE, Primary Examiner R. R. KUCIA, Assistant Examiner US. Cl. X.R. 

